ARM: phyCORE-i.MX8M SOM support

The phyCORE-i.MX8M aka PCL-066 is a SoM containing a i.MX8M SoC.

phyCORE-i.MX8M:
 - 1GB LPDDR4 RAM
 - eMMC
 - microSD
 - Ethernet

Signed-off-by: Christian Hemp <christian.hemp@posteo.de>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 120 insertions, 0 deletions

diff --git a/arch/arm/boards/phytec-som-imx8mq/lowlevel.c b/arch/arm/boards/phytec-som-imx8mq/lowlevel.c
new file mode 100644
index 0000000000..cfee13f3e7
--- /dev/null
+++ b/arch/arm/boards/phytec-som-imx8mq/lowlevel.c
@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2018 Christian Hemp
+ */
+
+#include <common.h>
+#include <linux/sizes.h>
+#include <mach/generic.h>
+#include <asm/barebox-arm-head.h>
+#include <asm/barebox-arm.h>
+#include <mach/imx8-ccm-regs.h>
+#include <mach/iomux-mx8.h>
+#include <mach/imx8-ddrc.h>
+#include <mach/xload.h>
+#include <io.h>
+#include <debug_ll.h>
+#include <asm/cache.h>
+#include <asm/sections.h>
+#include <asm/mmu.h>
+#include <mach/atf.h>
+#include <mach/esdctl.h>
+
+#include "ddr.h"
+
+extern char __dtb_imx8mq_phytec_phycore_som_start[];
+
+#define UART_PAD_CTRL	MUX_PAD_CTRL(PAD_CTL_DSE_3P3V_45_OHM)
+
+static void setup_uart(void)
+{
+	void __iomem *iomux = IOMEM(MX8MQ_IOMUXC_BASE_ADDR);
+	void __iomem *ccm   = IOMEM(MX8MQ_CCM_BASE_ADDR);
+
+	writel(CCM_CCGR_SETTINGn_NEEDED(0),
+	       ccm + CCM_CCGRn_CLR(CCM_CCGR_UART1));
+	writel(CCM_TARGET_ROOTn_ENABLE | UART1_CLK_ROOT__25M_REF_CLK,
+	       ccm + CCM_TARGET_ROOTn(UART1_CLK_ROOT));
+	writel(CCM_CCGR_SETTINGn_NEEDED(0),
+	       ccm + CCM_CCGRn_SET(CCM_CCGR_UART1));
+
+	imx_setup_pad(iomux, IMX8MQ_PAD_UART1_TXD__UART1_TX | UART_PAD_CTRL);
+
+	imx8_uart_setup_ll();
+
+	putc_ll('>');
+}
+
+static void phytec_imx8mq_som_sram_setup(void)
+{
+	enum bootsource src = BOOTSOURCE_UNKNOWN;
+	int instance = BOOTSOURCE_INSTANCE_UNKNOWN;
+	int ret = -ENOTSUPP;
+
+	ddr_init();
+
+	imx8_get_boot_source(&src, &instance);
+
+	if (src == BOOTSOURCE_MMC)
+		ret = imx8_esdhc_start_image(instance);
+
+	BUG_ON(ret);
+}
+
+/*
+ * Power-on execution flow of start_phytec_phycore_imx8mq() might not be
+ * obvious for a very first read, so here's, hopefully helpful,
+ * summary:
+ *
+ * 1. MaskROM uploads PBL into OCRAM and that's where this function is
+ *    executed for the first time
+ *
+ * 2. DDR is initialized and full i.MX image is loaded to the
+ *    beginning of RAM
+ *
+ * 3. start_phytec_phycore_imx8mq, now in RAM, is executed again
+ *
+ * 4. BL31 blob is uploaded to OCRAM and the control is transfer to it
+ *
+ * 5. BL31 exits EL3 into EL2 at address MX8MQ_ATF_BL33_BASE_ADDR,
+ *    executing start_phytec_phycore_imx8mq() the third time
+ *
+ * 6. Standard barebox boot flow continues
+ */
+ENTRY_FUNCTION(start_phytec_phycore_imx8mq, r0, r1, r2)
+{
+	arm_cpu_lowlevel_init();
+
+	if (IS_ENABLED(CONFIG_DEBUG_LL))
+		setup_uart();
+
+	if (get_pc() < MX8MQ_DDR_CSD1_BASE_ADDR) {
+		/*
+		 * We assume that we were just loaded by MaskROM into
+		 * SRAM if we are not running from DDR. We also assume
+		 * that means DDR needs to be initialized for the
+		 * first time.
+		 */
+		phytec_imx8mq_som_sram_setup();
+	}
+	/*
+	 * Straight from the power-on we are at EL3, so the following
+	 * code _will_ load and jump to ATF.
+	 *
+	 * However when we are re-executed upon exit from ATF's
+	 * initialization routine, it is EL2 which means we'll skip
+	 * loadting ATF blob again
+	 */
+	if (current_el() == 3) {
+		const u8 *bl31;
+		size_t bl31_size;
+
+		get_builtin_firmware(imx8mq_bl31_bin, &bl31, &bl31_size);
+		imx8mq_atf_load_bl31(bl31, bl31_size);
+	}
+
+	/*
+	 * Standard entry we hit once we initialized both DDR and ATF
+	 */
+	imx8mq_barebox_entry(__dtb_imx8mq_phytec_phycore_som_start);
+}